1. Field of the Invention
The present invention relates to: an ultrasonic image processing apparatus configured to obtain the motion state of a subject by using an ultrasonic image of the subject having been acquired with ultrasonic waves; and a method for processing an ultrasonic image.
2. Description of the Related Art
It is extremely important to objectively and quantitatively evaluate the functions of living body tissues such as the myocardium of a heart, for diagnoses of these living body tissues. For example, a quantitative evaluation method based on image data by acquiring image data of a heart using an ultrasonic imaging apparatus has been proposed.
For example, a method of obtaining motion information such as displacement and strain of a tissue by tracking the speckle pattern of images has been proposed (U.S. Pat. No. 6,638,221). This method, in which pattern matching is performed by using the speckle pattern of images, is referred to as Speckle Tracking (ST). From hereon, this method is sometimes referred to as the ST method.
For concrete example, in the case of evaluation of the function of the myocardium of a heart, ultrasonic waves are transmitted to the heart, whereby a plurality of tomographic image data acquired at different times are acquired. Then, by performing pattern matching of the endocardium of the heart by the ST method, it is possible to obtain wall motion information such as displacement and strain of the endocardium.
Further, a method of detecting the boundary between a tissue region and a blood region based on luminance information of an image and detecting the position of the boundary in real time has been proposed (Ultrasonic Imaging 5, 300-307(1983)). This method is referred to as the Acoustic Quantification (AQ) method. From hereon, this method is sometimes referred to as the AQ method.
However, in the abovementioned method of detecting the boundary in real time, only the contour of the tissue region is detected, but, for example, the movement of each point on the endocardium is not tracked. Therefore, vector information indicating the movement of each point on the endocardium cannot be obtained. As a result, it is impossible to analyze the wall motion of the myocardium.
On the other hand, by the abovementioned ST method, it is possible to acquire, for example, vector information indicating the movement of each point on the endocardium, and therefore, it is possible to analyze the wall motion of the myocardium. However, an operator needs to designate the boundary position of a region of interest (ROI) to be a tracking object, in a specific time phase. Therefore, it is difficult to analyze the motion of the region of interest in real time. For example, in a case where the contour of the endocardium is tracked, a tomographic image (a still image) acquired in a predetermined phase is displayed, and the operator needs to designate the boundary position of the endocardium while observing the tomographic image. Therefore, it is difficult to analyze the wall motion of the endocardium in real time.
Further, even the method stated in U.S. Pat. No. 6,638,221 has not been disclosed a concrete method for displaying motion information of a region of interest by the ST method.
As described above, in the conventional technique, it is difficult to analyze and display the motion of a region of interest in real time by using the vector information.